The computer database behind the government's controversial ID card scheme will be an amalgamation of existing IT networks, rather then one built from scratch, John Reid announced today.

But he insisted that this did not amount to a U-turn.

Originally, the record system, known as the national identity register, was to have been entirely newly-built, in order to avoid contamination from errors in existing database files on individuals.

But, in a 33-page progress report on the timetable for an identity card scheme, the home secretary revealed that instead the database would be compiled from amalgamated information from three separate Whitehall databases.

The information will be split between computers at the Department for Work and Pensions, the Home Office and the immigration and passport service.

Mr Reid said: "Doing something sensible is not necessarily a U-turn.

"We have decided it is lower risk, more efficient and faster to take the infrastructure that already exists, although the data will be drawn from other sources."

The "action plan" announced today would also see the creation next year of 69 regional offices for citizens to supply their biometric and iris details.

Some of these could be provided by the private sector, the Home Office document suggests.

Despite claims from critics that the bill for ID cards will balloon to £20bn eventually, today's report insists that the costs over the next decade will only be £5.4bn.

However, new costings will be placed before parliament next April, and updated regularly thereafter.

The plan also suggests that the ID card itself, which will initially be manufactured in-house by the Home Office, should be compatible with chip-and-pin technology, and that the database will not be connected directly to the internet, to prevent hacking.

Any interference with the database will carry a maximum 10-year prison sentence.

An independent commissioner will report back to the home secretary and to parliament on the implementation and any abuses of the NIR.

The piecemeal implementation of a national ID card scheme is unaltered by the action plan, although the report is hedged with provisos and caveats.

The foreword admits that the scheme "will evolve over time", and that "we shall adjust the details of this action plan as required by experience".

New primary legislation would be required to make carrying an identity card compulsory, but at present the timetable will see some foreign nationals required to register for biometric details next year, the first "voluntary" ID cards issued alongside passports from 2009.

Concurrent with the action plan, Mr Reid also announced proposals to force foreigners already in the UK to register their biometrics, such as fingerprints and iris scans.

"We are going to look at how we could do it for people who are already here," he said.

The immigration minister, Liam Byrne, said that a consultation paper would be published in the new year.

Mr Reid said that today's action plan was "the starting gun for the national identity scheme". He insisted that it would be a "critical national investment" for the UK.

It would help secure Britain's borders and tackle illegal immigration, reduce fraud, fight crime and terrorism, and improve protection for children and for other vulnerable people by providing a secure means of identification, he said.

The home secretary said: "No one who opposes introduction of identity management can truly claim to treat these subjects as seriously as they claim to do."

But critics have pointed out that the rationale behind the ID card scheme - which is opposed by both the Conservatives and Liberal Democrats - has expanded from anti-terrorism to cover identity theft, fraud, benefits provision and healthcare.

David Davis, the shadow home secretary, called the scheme an "expensive white elephant" that risked making Britain less safe.

He said: "The use of existing databases is an admission of what will turn out to be a financial disaster for the taxpayer, with a cost overrun of billions of pounds due to badly designed, costly systems.

"The fact Dr. Reid has tried to sneak this announcement out in a written statement that is not subject to scrutiny betrays just how fragile the government's confidence in their own scheme actually is."

"What we now have is a designer database targeted solely at those who obey the law. Illegal immigrants will not turn up to apply for visas and submit their biometrics.

"Terrorists stopped in the street will not be carrying ID cards and are highly unlikely to pop into the police station the next day with their papers.

Phil Booth, the national coordinator of the NO2ID campaign group, said: "This is pretty appalling. Rather than a single, highly-secure database that David Blunkett and Charles Clarke promised the nation, the Home Office is now saying we are simply going to designate people's data which is mixed in with other data."

He also claimed that children as young as 11 will have to be fingerprinted and have their irises read for the scheme.

The Liberal Democrat home affairs spokesman, Nick Clegg, said: "These are sticking plaster measures in which the government is cutting corners to make the increasingly unpopular ID card scheme more palatable.

"The fact remains that however much John Reid rearranges the deckchairs, ID cards are doomed to be unacceptably expensive, intrusive and unmanageable."